Follow Bgunner's advice and be sure you don't have a wiring problem, but I wouldn't be surprised if the valve is in fact bad. That would be very easy to replace, shouldn't be super hard to bleed. My brother used to have an Airbag Code 41 which normally means resistance in circuit wire, open circuit, or crash sensor, turned out the computer was actually junk... so definitely worth ruling out that you don't have a wiring problem first, but replacing the valve (ABS hydraulic unit) would be pretty straightforward. +1 on CARDONE unit, cheapest I've seen
If your truck is OBD2 (I don't remember what year you said it is) I believe some very advanced scanners can perform a bleed procedure for you on the ABS system (it would just pump the valve), pre OBD2 requires an OBS ford tool (very expensive, OR:
Replace valve, slam brakes repeatedly on gravel or dirt road, should cause ABS to try to engage and use the ABS hydraulic unit valves to pump air out of ABS unit for you, then you need to bring truck home and re bleed all four corners (but really rear) as normal, OR:
I don't see why you couldn't buy a spare electrical connector for the RABS unit on your frame rail, identify power and ground, energize connector with a spare 12v battery, should pump the ABS unit for you right there in driveway or garage, bleed at wheels, repeat as necessary.